Sub-nanosecond radially polarized light is obtained by using passively Q-switching of Nd∶YAG/Cr4+∶YAG bounding crystal and S-waveplate. The pulsed diode laser end pumping method with peak power of 30 W, pulse width of 120 μs, repetition frequency of 1 kHz, is used to obtain Q-switched laser pulse output with pulse width of 878 ps and single pulse energy of 76.8 μJ. The repetition frequency instability is less than ±0.003% and the amplitude instability is less than ±3%. By inserting the polarizer and S-wave plate after bonding crystal, a sub-nanosecond radially polarized light with purity of more than 96% and single pulse energy of 27.5 μJ is obtained.